Method for sterilizing gas containers and filling same with a sterile gas

ABSTRACT

One or more gas containers connected by a conduit means to a feed source are sterilized and sterilely filled by the evacuation of the containers and conduit means to a low pressure, the introduction of a sterilizing agent into the containers and conduit means for a suitable holding period, the removal of the sterilizing agent by a further evacuation of the containers and conduit means, and the introduction of a gaseous feed stock to the containers through a sterilizing unit in the conduit means.

United States Patent I 1 1 3,620,265

[72] inventors Gordon N. Strople 156] References Cited chefry UNITED STATES PATENTS #3 Mills cinmmimni 2.054.093 9/1936 M1115 .1. 99/251 {21] AppLNo. 53,394 2.891.838 6/1959 Kaye 21/58 2,938,766 5/1960 Hall 21/58 [22] F11ed July 9, 1970 3,206,275 9/1965 Salr et al 21/58 [45] Patented 3 393 491 7/1968 Burton et a1 141/11x [73] Assignee Lif-O-Gen, Inc.

Lumberton, NJ. Primary Examiner Laverne D. Geiger Continuation-impart of application Ser. No. Assistant xam ner-Edward J. Earls 765,004, Oct. 4, 1968, now abandoned. A110 and This application July 9, 1970, Ser. No. 053,394

[54] METHOD FOR STERILIZING GAS CONTAINERS AND FILLING SAME WITH A STERILE GAS ABSTRACT: One or more gas contalners connected by a conduit means to a feed source are sterilized and sterilely filled by 2 Chums 1 Drawing the evacuation of the containers and conduit means to a low [52] U.S. Cl 141/8, 1 pressure. the introduction of a sterilizing agent into the con- 21/58, 21/78, 141/63, 141/92 1 tainers and conduit means for a suitable holding period. the

[51 lnt. Cl 8651) 55/02 removal of the sterilizing agent by a further evacuation of the [50] Field of Search 21/58. 78; 3 containers and conduit means. and the introduction ofa gase' 53/12; 99/21 1. 214, 249. 251. 252; l4l/l.4, 6-9, 1 ous feed stock to the containers through a sterilizing unit in 11. 61. 63. 65, 66. 69, 85. 91, 92 1 the conduit means.

Eff/PIA an PATENTEDuuv 16 I97! mvENroRs: GORDON N ST ROPLE BY JUSTIN W. MILLS,JR. v WW ATTYS METHOD FOR STERILIZING GAS CONTAINERS AND FILLING SAME WITH A STERILE GAS This application is a continuation-impart of our copending application Ser. No. 765,044,filed Oct. 4, 1968 entitled Method and Apparatus for Sterilizing Gas Containers and Filling Same with a Sterile Gas, now abandoned.

The present invention relates generally to the packaging of gaseous products and relates more particularly to a method and apparatus for effectively eliminating micro-organisms from gas containers and the gaseous products introduced thereinto.

There are many situations in which a gaseous product is desirably provided in a sterile condition. An obvious example is the field of medicine wherein respiratory gases should be in a sterile state prior to administration to a patient. Similarly, compressed gases used to power surgical devices and gases used as propellants in drug aerosol packaging should be free from contaminants. There are in addition many laboratory and industrial situations such as space simulation chambers, and industrial clean rooms in which the sterility of a gaseous stock is desirable.

Gaseous products are readily available at purities exceeding 99.999 percent, and methods are also available to analyze gases to such a high degree of accuracy. However, the methods conventionally employed for gas analysis, including mass spectrometry, spectrophotometry, gas chromatography and wet chemistry, will not detect bacteria or viruses even if present in a gas in large quantities. It is commonly thought that the cryogenic processes normally utilized to produce atmospheric gases and/or the high pressures at which they are stored and packaged serve to sterilize the gases. However, the extremely low temperatures may only cause bacteria to become dormant and high pressures per se do not have a sterilizing effect. There are a number of well-known methods for sterilizing gases and also for sterilizing gas containers. Until the present invention, however, there has not been a satisfactory method and apparatus for charging one or more gas containers with a gaseous feed stock which effectively insures the sterilization of both the containers and their contents. Since Federal regulations prohibit the shipment of conventional pressurized containers unless safety relief valves are provided which are sensitive to temperature (212 F.) and pressure (2.265 p.s.i.g.), the containers cannot during sterilization and filling be subjected to conditions of temperature and pressure which exceed these limits.

- The present process in brief involves the connection of a plurality of empty gas containers to a conduit means connecting the containers with a gaseous feed stock. The containers and the conduit means are then evacuated to a low pressure following which the containers and conduit means are filled with a sterilizing agent for a predetermined holding period to effect a sterilization of both the containers and the conduit means. The sterilizing agent is then evacuated from the containers and conduit means, and the gaseous feed stock is introduced to the containers through a suitable filtering means in the conduit means which may for example comprise a submicron filter. The container valves are then closed, and the filled containers are disconnected from the conduit means. All of the above steps are carried out with the containers sealed against the entrance of ambient air and at a temperature below 2 l 2 F.

It is accordingly a primary object of the present invention to provide a method and apparatus for the sterile packaging of gases and gaseous mixtures. I

A further object of the invention is to provide a method and apparatus as described which can be utilized for the simultaneous sterile filling of a large number of gas containers.

A still further object of the invention is to provide a method and apparatus as described which are adapted for the sterile filling of a plurality of containers at a relatively rapid rate and with low initial and operating costs.

Additional objects and advantages of the invention will be more readily apparent from the following detailed description of an embodiment thereof when taken together with the accompanying drawing which is a schematic illustration of apparatus in accordance with the present invention for providing a sterilized filling of a plurality of containers with a gaseous feed stock.

Referring to the drawing, an apparatus is illustrated for sterilizing a plurality of gas containers l0 and filling said containers with a sterile gaseous feed stock which is supplied from a storage tank 12 and suitably sterilized. The gas containers [0 may for example be made of steel in a cylindrical shape and include a valve 14 at the upper end thereof which is connected to the neck of the container in a gastight seal. Conventional temperature and pressure relief valves (not shown) are provided on each container as required by Department of Transportation regulations for pressurized vessels. The containers 10 are connected to a charging manifold 16 by tubes 18 extending between the container valves 14 and spaced outlets 20 of the manifold. The manifold at its left-hand end 24 opens into a humidity and temperature control unit 26 through which it connects by means of a conduit 28 with the vertical conduit 30.

The feed stock tank 12, which includes a valve 32 at its upper end, is connected to a conduit 34 by tube 36. The conduit 34 leads into a compressor 38 driven by motor 40. The outlet of the compressor 38 opens into a sterilizer 42 which is in turn connected with the lower end of the conduit 30. A valve 44 is provided between the compressor 38 and the sterilizer 42. An additional gas tank 46 filled with a diluent gas such as carbon dioxide is connected with the conduit 34 by means of tube 50. A valve 52 on the tank 46 pennits control of the diluent gas flow.

A conduit 54 which opens into the conduit 30 at 56 is coupled to tanks 58 containing a sterilizing agent by connecting tubes 60. Valves 62 on the tanks 58 permit control of the flow of sterilizing agent from the tanks.

The upper end of conduit 30 leads into a sterilizer 64 to the opposite side of which is connected a vacuum pump 66 driven by a motor 68. A vacuum gauge 70 is provided between the vacuum pump and sterilizer, and a valve 72 is included in the conduit 30 between the sterilizer and the juncture 56 with the conduit 54. A pressure gauge 74 is located in the conduit 30 between the valves 44 and 72 to indicate the pressure and hence the amount of gas in the containers 10.

The sterilizer units 42 and 64 in a typical embodiment of the invention, for example, may comprise submicron filter media having a screen opening size of about 0.4 microns. A commercially available filter suitable for this purpose is manufactured by the Cox Instrument Corporation, Model 430 Filter Element CBAA. 45. It is also desirable to include in each filter unit a primary filter which is preferably a lO-micron filter to remove larger particles of contamination.

Sterilization as defined by the American Medical Association is an absolute term meaning the complete destruction or removal of all forms of life, i.e., the absence or destruction of all micro-organisms, and the term sterilizing agent as used in this specification means an agent which will accomplish sterilization in accordance with this definition. Thus the sterilizing agent in a typical embodiment of the invention may be ethylene oxide which is most effectively employed in the flammable range (3-400 percent by volume in air). Concentrations approaching I00 percent are preferred but must be diluted prior to evacuation to atmosphere to eliminate the danger of explosion or fire.

To carry out the present process utilizing the abovedescribed apparatus, the empty gas containers 10 to be filled with the feed stock are connected to the charging manifold by tubes 18 to seal the container against the entrance of ambient air and the valves 14 thereof are opened. with the valves 32, 44, 52 and 62 being closed. the valve 72 is opened and a high vacuum is drawn on the entire system by means of the pump 66. By evacuating the gas containers l0 and the various conduits of the system, virtually all airborne contaminants are removed from the containers and the system. The valve 72 is then closed, the pump 66 shut off and valves 62 are opened to permit the sterilizing agent to pass into the containers as well as the conduit system. Valves 62 are then closed after a predetermined amount of sterilizing agent has been admitted into the containers and the conduit system. The sterilizing agent is allowed to remain in the system for a suitable holding period, and the concentration, humidity and temperature are accurately controlled in a well-known manner to insure an effective sterilization of the containers 10 as well as the system conduits.

The period required for the effective sterilization of the containers and the conduit system will depend not only on the sterilizing agent used, the concentration of the agent, and the temperature, pressure and humidity conditions within the system, but also on such variables as the condition of the containers, and the size of the system. A typical example of effective sterilization is as follows: an 88 percent concentration of ethylene oxide at 78 F. with a humidity of 40 percent and a holding period of 1 hour at about 1 atmosphere.

When the sterilizing agent has remained in the system for the required holding time, the valve 72 is opened and the pump 66 again employed to evacuate the sterilizing agent from the system. Since the sterilizing agent may be utilized in a flammable concentration, it may first be necessary before evacuation to inject an inert diluent gas such as carbon dioxide into the system from the container 48 by opening valves 44 and 52. When the gas mixture in the system reaches a safe concentration, the valve 52 is closed and the valve 72 is opened to permit a safe evacuation of the gas mixture. To insure a complete removal of the sterilizing agent, a high vacuum is preferably drawn on the containers and conduit system by the pump 66.

When the sterilizing agent and diluent gas have been removed from the container 10 and the conduit system, the valve 72 is closed and the valves 32 and 44 are opened to permit passage of the feed stock through the conduit 34 into the sterilizer 42, thence through conduits 30 and 28 into manifold 16 and into the several containers 10. When the containers 10 have been filled to the desired pressure as indicated by the gauge 74, the container valves 14 are closed, the valve 32 on the feed stock tank 12 is closed and the containers 10 may be disconnected from the tubes 18 and are ready for packaging and shipment. A sample may be taken from one of the containers l and tested to insure the sterile condition of the gas.

During the entire sterilizing and filling process, the containers are maintained at a temperature below 2 1 2 F. and at a pressure below 2,265 p.s.i.g. to prevent the opening of the temperature and pressure-sensitive relief valves built into the containers.

The compressor 38 is available for use in transferring gas products from the tanks 12 and 46 into the conduit system and containers to the desired pressure.

The sterilizer 64 may be of the same type and construction as the sterilizer 42 and is provided to prevent recontamination of the system by the entrance or reentrance of contaminants into the system, for example, in the event of failure of the vacuum pump 66 which would permit a feed back into the charging system.

in the process described above, it is not essential that a complete evacuation of the system be effected prior to the addition of the sterilizing agent since the sterilizing agent would act on airborne contaminants as well as those on the surfaces of the system and containers. However, in the preferred process a high vacuum is initially drawn to eliminate all airborne matter.

Although submicron filters have been described as one fonn of a suitable sterilizing means, other methods of sterilizing the feed stock can be employed.

The, term gas as used with reference to the feed stock, sterilizing agent and diluent for the sterilizing agent R refers to fluids which at atmospheric pressure are normally in the gaseous state. it should be understood, however, that at elevated pressures, these fluids may be in the liquid stage and that the invention is not in any way affected by the stage or change of sta e of these fluids.

rom the foregomg the Invention can be understood to provide a method and apparatus for effecting the sterilization of one or more containers and filling of the sterilized container with a sterile gas without contaminating the container. The filled container is placed in a sealed enclosure containing a sterilizing agent to effect and maintain a sterilization of the exterior of the container until ready for use.

Manifestly, changes in details of construction can be effected by those skilled in the art without departing from the spirit and scope of the invention as defined in and limited solely by the appended claims.

We claim:

1. A sterilizing and packaging method for providing a container of compressed sterile gas suitable for medical use and food, drug and cosmetic packaging, said container having closure means thereon, which method comprises maintaining a selected container sealed against the entrance of ambient air and contaminants and at a temperature below 2l2 F., and while maintaining said container so sealed performing the steps of evacuating the container via said closure means to completely remove therefrom all traces of ambient air, introducing into said evacuated container via said closure means a gaseous sterilizing agent capable of destroying all micro-organisms therein to sterilize the interior of said container, maintaining said sterilizing agent in the container for a predetermined holding period sufficient to destroy all microorganisms in said container, evacuating said container via said closure means to remove therefrom all traces of said sterilizing agent, sterilizing a selected compressed gas to remove all micro-organisms therefrom, introducing a predetermined quantity of the sterilized compressed gas into said sterilized container via said closure means, and closing the closure means for said sterilized container to maintain the sterilized gas therein in a sterile condition.

2. The method claimed in claim 1 wherein the gaseous sterilizing agent is flammable and including the step of introducing into the sterilizing agent while in the container a sterile inert gas in sufiicient quantity to dilute the sterilizing agent to a nonflammable concentration. 

1. A sterilizing and packaging method for providing a container of compressed sterile gas suitable for medical use and food, drug and cosmetic packaging, said container having closure means thereon, which method comprises maintaining a selected container sealed against the entrance of ambient air and contaminants and at a temperature below 212* F., and while maintaining said container so sealed performing the steps of evacuating the container via said closure means to completely remove therefrom all traces of ambient air, introducing into said evacuated container via said closure means a gaseous sterilizing agent capable of destroying all micro-organisms therein to sterilize the interior of said container, maintaining said sterilizing agent in the container for a predetermined holding period sufficient to destroy all micro-organisms in said container, evacuating said container via said closure means to remove therefrom all traces of said sterilizing agent, sterilizing a selected compressed gas to remove all micro-organisms therefrom, introducing a predetermined quantity of the sterilized compressed gas into said sterilized container via said closure means, and closing the closure means for said sterilized container to maintain the sterilized gas therein in a sterile condition.
 2. The method claimed in claim 1 wherein the gaseous sterilizing agenT is flammable and including the step of introducing into the sterilizing agent while in the container a sterile inert gas in sufficient quantity to dilute the sterilizing agent to a nonflammable concentration. 